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EE 359: Wireless Communications

EE 359: Wireless Communications. Professor Andrea Goldsmith. Next-Gen Cellular/ WiFi Smart Homes/Spaces Autonomous Cars Smart Cities Body-Area Networks Internet of Things All this and more …. Outline. Course Basics Course Syllabus Wireless History The Wireless Vision

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EE 359: Wireless Communications

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  1. EE 359: Wireless Communications Professor Andrea Goldsmith Next-Gen Cellular/WiFi Smart Homes/Spaces Autonomous Cars Smart Cities Body-Area Networks Internet of Things All this and more …

  2. Outline • Course Basics • Course Syllabus • Wireless History • The Wireless Vision • Technical Challenges • Current/Next-Gen Wireless Systems • Spectrum Regulation and Standards • Emerging Wireless Systems (Optional Lecture)

  3. Course Information* People • Instructor: Andrea Goldsmith, Pack 371, andrea@ee, OHs: TThimmediately after class and by appt. • TAs: Tom Dean (trdean@stanford.edu) and Milind Rao (milind@Stanford.edu) • Discussion section: Wed 4-5 pm (hopefully taped) • OHs: Wed 5-6pm, Fri 10-11am (Tom), Thu 4-5pm (Milind). Email OHs: Thu 5-6pm (Milind), Fri 11am-12pm (Tom). Email OHs are ideally via Piazza. • Piazza: https://piazza.com/stanford/fall2015/ee359/home. all are registered, will use to poll on OH/discussion times • Class Administrator: Julia Gillespie, jvgill@stanford, Packard 365, 3-2681. Homework dropoff: Fri by 4 pm. *See web or handout for more details

  4. Course InformationNuts and Bolts • Prerequisites: EE279 or equivalent (Digital Communications) • Required Textbook: Wireless Communications (by me), CUP • Available at bookstore (out of stock) or Amazon • Extra credit for finding typos/mistakes/suggestions (2nd ed. soon!) • Supplemental texts at Engineering Library. • Class Homepage: www.stanford.edu/class/ee359 • All announcements, handouts, homeworks, etc. posted to website • “Lectures” link continuously updates topics, handouts, and reading • Calendar will show any changes to class/OH/discussion times • Class Mailing List: ee359-aut1617-students@lists (automatic for on-campus registered students). • Guest list ee359-aut1617-guest@lists for SCPD and auditors: send Milind/Mainak email to sign up. • Sending mail to ee359-aut1617-staff@listsreaches me and TAs.

  5. Course InformationPolicies • Grading: Two Options • No Project (3 units): HW – 25%, 2 Exams – 35%, 40% • Project (4 units): HWs- 20%, Exams - 25%, 30%, Project - 25% • HWs: assigned Thu, due following Fri 4pm (starts 9/29) • Homeworks lose 33% credit after 4pm Fri, lowest HW dropped • Up to 3 students can collaborate and turn in one HW writeup • Collaboration means all collaborators work out all problems together • Unpermitted collaboration or aid (e.g. solns for the book or from prior years) is an honor code violation and will be dealt with strictly. • Extra credit: up to 2 “design your own” HW problems; course eval • Exams: • Midterm week of 11/6. (It will be scheduled outside class time; the duration is 2 hours.) Final on 12/13 from 12:15-3:15pm. • Exams must be taken at scheduled time (with very few exceptions)

  6. Course InformationProjects • The term project (for students electing to do a project) is a research project related to any topic in wireless • Two people may collaborate if you convince me the sum of the parts is greater than each individually • A 1 page proposal is due 10/27 at midnight. • 5-10 hours of work typical for proposal • Must create project website and post proposal there (submit web link) • Preliminary proposals can be submitted for early feedback • The project is due by midnight on 12/9 (on website) • 20-40 hours of work after proposal is typical for a project • Suggested topics in project handout • Anything related to wireless or application of wireless techniques ok.

  7. Course Syllabus • Overview of Wireless Communications • Path Loss, Shadowing, and Fading Models • Capacity of Wireless Channels • Digital Modulation and its Performance • Adaptive Modulation • Diversity • MIMO Systems • Multicarrier Modulation and OFDM • Multiuser Systems • Cellular Systems

  8. Class Rescheduling • No lectures Tue 10/3, Tue 10/24, Thu 11/2 and Thu 11/30. • These lectures are rescheduled as follows: • Lecture Tue 10/3 rescheduled to Mon 10/2, 12-1:30pm, Thornton 102 with lunch • Lecture Tue 10/24 is rescheduled to Fri 10/20 10:30-11:50. Thornton 102 with donuts • Lecture Thu 11/2 will be rescheduled to Fri 11/3 or Wed 11/1 with food • Lecture Thu 11/30 will be rescheduled to Fri 12/1, Thornton 102 with donuts • Last lecture has an optional component 11:50-12:30 on advanced topics with lunch

  9. Wireless History • Ancient Systems: Smoke Signals, Carrier Pigeons, … • Radio invented in the 1880s by Marconi • Many sophisticated military radio systems were developed during and after WW2 • Exponential growth in cellular use since 1988: approx. 8B worldwide users today • Ignited the wireless revolution • Voice, data, and multimedia ubiquitous • Use in 3rdworld countries growing rapidly • Wifi also enjoying tremendous success and growth • Bluetooth pervasive, satellites also widespread

  10. Future Wireless Networks Ubiquitous Communication Among People and Devices Next-Gen Cellular/WiFi Smart Homes/Spaces Autonomous Cars Smart Cities Body-Area Networks Internet of Things All this and more …

  11. Challenges AdHoc • Network/Radio Challenges • Gbps data rates with “no” errors • Energy efficiency • Scarce/bifurcated spectrum • Reliability and coverage • Heterogeneous networks • Seamless internetwork handoff 5G BT Radio Short-Range GPS Cellular Cog • Device/SoC Challenges • Performance • Complexity • Size, Power, Cost • High frequencies/mmWave • Multiple Antennas • Multiradio Integration • Coexistance Mem WiFi CPU mmW

  12. Software-Defined (SD) Radio: Is this the solution to the device challenges? BT FM/XM A/D A/D A/D GPS Cellular A/D DVB-H DSP Apps Processor WLAN Media Processor Wimax Today, this is not cost, size, or power efficient SubNyquist sampling may help with the A/D and DSP requirements • Wideband antennas and A/Ds span BW of desired signals • DSP programmed to process desired signal: no specialized HW

  13. “Sorry America, your airwaves are full*” On the Horizon: “The Internet of Things” Exponential Mobile Data Growth Leading to massive spectrum deficit 50 billion devices by 2020 Source: FCC *CNN MoneyTech – Feb. 2012 14

  14. What is the Internet of Things: • Enabling every electronic device to be connected to each other and the Internet • Includes smartphones, consumer electronics, cars, lights, clothes, sensors, medical devices,… • Value in IoT is data processing in the cloud Different requirements than smartphones: low rates/energy consumption

  15. Are we at the Shannon limit of the Physical Layer? We are at the Shannon Limit • “The wireless industry has reached the theoretical limit of how fast networks can go” K. Fitcher, Connected Planet • “We’re 99% of the way” to the “barrier known as Shannon’s limit,” D. Warren, GSM Association Sr. Dir. of Tech. Shannon was wrong, there is no limit • “There is no theoretical maximum to the amount of data that can be carried by a radio channel” M. Gass, 802.11 Wireless Networks: The Definitive Guide • “Effectively unlimited” capacity possible via personal cells (pcells). S. Perlman, Artemis.

  16. What would Shannon say? We don’t know the Shannon capacity of most wireless channels • Channels with interference or relays. • Cellular systems • Ad-hoc and sensor networks • Channels with delay/energy/$$$ constraints. Shannon theory provides design insights and system performance upper bounds • Time-varying channels.

  17. Current/Next-Gen Wireless Systems • Current: • 4G Cellular Systems (LTE-Advanced) • 4G Wireless LANs/WiFi (802.11ac) • mmWave massive MIMO systems • Satellite Systems • Bluetooth • Zigbee • WiGig • Emerging • 5G Cellular and WiFi Systems • Ad/hoc and Cognitive Radio Networks • Energy-Harvesting Systems • Chemical/Molecular Much room For innovation

  18. BS Spectral Reuse In licensed bands and unlicensed bands Wifi, BT, UWB,… Cellular Reuse introduces interference Due to its scarcity, spectrum is reused

  19. BASE STATION Cellular Systems:Reuse channels to maximize capacity • Geographic region divided into cells • Freq./timeslots/codes/space reused in different cells (reuse 1 common). • Interference between cells using same channel: interference mitigation key • Base stations/MTSOs coordinate handoff and control functions • Shrinking cell size increases capacity, as well as complexity, handoff, … MTSO

  20. 4G/LTE Cellular • Much higher data rates than 3G (50-100 Mbps) • 3G systems has 384 Kbps peak rates • Greater spectral efficiency (bits/s/Hz) • More bandwidth, adaptive OFDM-MIMO, reduced interference • Flexible use of up to 100 MHz of spectrum • 10-20 MHz spectrum allocation common • Low packet latency (<5ms). • Reduced cost-per-bit (not clear to customers) • All IP network

  21. 5G Upgrades from 4G

  22. BS BS BS Future Cellular Phones Burden for this performance is on the backbone network Everything wireless in one device San Francisco Internet LTE backbone is the Internet Paris Nth-Gen Cellular Nth-Gen Cellular Phone System Much better performance and reliability than today - Gbpsrates, low latency, 99% coverage, energy efficiency

  23. Wifi NetworksMultimedia Everywhere, Without Wires 802.11ac • Streaming video • Gbpsdata rates • High reliability • Coverage inside and out Wireless HDTV and Gaming

  24. Many WLAN cards have (a/b/g/n) Wireless LAN Standards • 802.11b (Old – 1990s) • Standard for 2.4GHz ISM band (80 MHz) • Direct sequence spread spectrum (DSSS) • Speeds of 11 Mbps, approx. 500 ft range • 802.11a/g (Middle Age– mid-late 1990s) • Standard for 5GHz band (300 MHz)/also 2.4GHz • OFDM in 20 MHz with adaptive rate/codes • Speeds of 54 Mbps, approx. 100-200 ft range • 802.11n/ac/ax (current/next gen) • Standard in 2.4 GHz and 5 GHz band • Adaptive OFDM /MIMO in 20/40/80/160 MHz • Antennas: 2-4, up to 8 • Speeds up to 1 Gbps (10 Gbps for ax), approx. 200 ft range • Other advances in packetization, antenna use, multiuser MIMO

  25. Why does WiFi performance suck? Carrier Sense Multiple Access: if another WiFi signal detected, random backoff Collision Detection: if collision detected, resend • The WiFi standard lacks good mechanisms to mitigate interference, especially in dense AP deployments • Multiple access protocol (CSMA/CD) from 1970s • Static channel assignment, power levels, and carrier sensing thresholds • In such deployments WiFi systems exhibit poor spectrum reuse and significant contention among APs and clients • Result is low throughput and a poor user experience • Multiuser MIMO will help each AP, but not interfering APs

  26. Self-Organizing Networks for WiFi - Channel Selection - Power Control - etc. SoN Controller • SoN-for-WiFi: dynamic self-organization network software to manage of WiFi APs. • Allows for capacity/coverage/interference mitigation tradeoffs. • Also provides network analytics and planning.

  27. Satellite Systems • Cover very large areas • Different orbit heights • GEOs (39000 Km) versus LEOs (2000 Km) • Optimized for one-way transmission • Radio (XM, Sirius) and movie (SatTV, DVB/S) broadcasts • Most two-way systems went bankrupt • Global Positioning System (GPS) ubiquitous • Satellite signals used to pinpoint location • Popular in cell phones, PDAs, and navigation devices

  28. Bluetooth • Cable replacement RF technology (low cost) • Short range (10m, extendable to 100m) • 2.4 GHz band (crowded) • 1 Data (700 Kbps) and 3 voice channels, up to 3 Mbps • Widely supported by telecommunications, PC, and consumer electronics companies • Few applications beyond cable replacement 8C32810.61-Cimini-7/98

  29. IEEE 802.15.4/ZigBee Radios • Low-rate low-power low-cost secure radio • Complementary to WiFi and Bluetooth • Frequency bands: 784, 868, 915 MHz, 2.4 GHz • Data rates: 20Kbps, 40Kbps, 250 Kbps • Range: 10-100m line-of-sight • Support for large mesh networking or star clusters • Support for low latency devices • CSMA-CA channel access • Applications: light switches, electricity meters, traffic management, and other low-power sensors.

  30. Spectrum Regulation • Spectrum a scarce public resource, hence allocated • Spectral allocation in US controlled by FCC (commercial) or OSM (defense) • FCC auctions spectral blocks for set applications. • Some spectrum set aside for universal use • Worldwide spectrum controlled by ITU-R • Regulation is a necessary evil. Innovations in regulation being considered worldwide in multiple cognitive radio paradigms

  31. Standards • Interacting systems require standardization • Companies want their systems adopted as standard • Alternatively try for de-facto standards • Standards determined by TIA/CTIA in US • IEEE standards often adopted • Process fraught with inefficiencies and conflicts • Worldwide standards determined by ITU-T • In Europe, ETSI is equivalent of IEEE Standards for current systems are summarized in Appendix D.

  32. Advanced Topics Lecture Emerging Systems • New cellular system architectures • mmWave/massive MIMO communications • Software-defined network architectures • Ad hoc/mesh wireless networks • Cognitive radio networks • Wireless sensor networks • Energy-constrained radios • Distributed control networks • Chemical Communications • Applications of Communications in Health, Bio-medicine, and Neuroscience

  33. Rethinking “Cells” in Cellular • How should cellular • systems be designed for • Capacity • Coverage • Energy efficiency • Low latency • Traditional cellular design “interference-limited” • MIMO/multiuser detection can remove interference • Cooperating BSs form a MIMO array: what is a cell? • Relays change cell shape and boundaries • Distributed antennas move BS towards cell boundary • Small cells create a cell within a cell • Mobile cooperation via relays, virtual MIMO, network coding. Coop MIMO Small Cell Relay DAS

  34. Dozens of devices mmWave Massive MIMO 10s of GHz of Spectrum Hundreds of antennas • mmWaves have large non-monotonic path loss • Channel model poorly understood • For asymptotically large arrays with channel state information, no attenuation, fading, interference or noise • mmWave antennas are small: perfect for massive MIMO • Bottlenecks: channel estimation and system complexity • Non-coherent design holds significant promise

  35. Software-Defined Network Architectures App layer Cloud Computing Video Security Vehicular Networks M2M Health Freq. Allocation Power Control Self Healing ICIC QoS Opt. CS Threshold Network Optimization UNIFIED CONTROL PLANE HW layer mmWave WiFi Cellular Ad-Hoc Networks … Distributed Antennas

  36. Ad-Hoc Networks • Peer-to-peer communications • No backbone infrastructure or centralized control • Routing can be multihop. • Topology is dynamic. • Fully connected with different link SINRs • Open questions • Fundamental capacity region • Resource allocation (power, rate, spectrum, etc.) • Routing

  37. Cognitive Radios NCR NCR MIMO Cognitive Underlay Cognitive Overlay IP CR CR CRRx CRTx NCRRx NCRTx • Cognitive radios support new users in existing crowded spectrum without degrading licensed users • Utilize advanced communication and DSP techniques • Coupled with novel spectrum allocation policies • Multiple paradigms • (MIMO) Underlay (interference below a threshold) • Interweave finds/uses unused time/freq/space slots • Overlay (overhears/relays primary message while cancelling interference it causes to cognitive receiver)

  38. Wireless Sensor Networks Data Collection and Distributed Control • Smart homes/buildings • Smart structures • Search and rescue • Homeland security • Event detection • Battlefield surveillance • Energy (transmit and processing) is the driving constraint • Data flows to centralized location (joint compression) • Low per-node rates but tens to thousands of nodes • Intelligence is in the network rather than in the devices

  39. Energy-Constrained Radios • Transmit energy minimized by sending bits slowly • Leads to increased circuit energy consumption • Short-range networks must consider both transmit and processing/circuit energy. • Sophisticated encoding/decoding not always energy-efficient. • MIMO techniques not necessarily energy-efficient • Long transmission times not necessarily optimal • Multihop routing not necessarily optimal • Sub-Nyquist sampling can decrease energy and is sometimes optimal!

  40. Whereshouldenergy come from? • Batteries and traditionalchargingmechanisms • Well-understooddevices and systems • Wireless-power transfer • Poorlyunderstood, especially at large distances and with high efficiency • Communication withEnergyHarvesting Radios • Intermittent and randomenergyarrivals • Communication becomesenergy-dependent • Can combine information and energy transmission • New principles for radio and network design needed.

  41. Distributed Control over Wireless Automated Vehicles - Cars - Airplanes/UAVs - Insect flyers Interdisciplinary design approach • Control requires fast, accurate, and reliable feedback. • Wireless networks introduce delay and loss • Need reliable networks and robust controllers • Mostly open problems : Many design challenges

  42. Chemical Communications • Can be developed for both macro (>cm) and micro (<mm) scale communications • Greenfield area of research: • Need new modulation schemes, channel impairment mitigation, multiple acces, etc.

  43. Applications in Health, Biomedicine and Neuroscience • Neuroscience • Nerve network (re)configuration • EEG/ECoGsignal processing • Signal processing/control for deep brain stimulation • SP/Comm applied to bioscience Body-Area Networks Recovery from Nerve Damage ECoG Epileptic SeizureLocalization EEG ECoG

  44. Main Points • The wireless vision encompasses many exciting applications • Technical challenges transcend all system design layers • 5G networks must support higher performance for some users, extreme energy efficiency and/or low latency for others • Cloud-based software to dynamically control and optimize wireless networks needed (SDWN) • Innovative wireless design needed for 5G cellular/WiFi, mmWave systems, massive MIMO, and IoT connectivity • Standards and spectral allocation heavily impact the evolution of wireless technology

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